
1. Field of the Invention
The present invention relates to a method for determining the waviness of a surface, and more particularly to a method for predicting gaps between mating surfaces of an assembly due to waviness of the surface.
2. Background Art
Surface profiling instruments, such as profilometers, are used to measure a profile of a surface. Raw data obtained by the surface profiling instrument is filtered to produce data indicative of surface finish quality. One type of data that can be extracted is known as waviness, which focuses on longer wavelength undulations of the surface.
A waviness parameter known as WT measures the maximum peak to valley height of the surface over a sampled distance. Prior filtering techniques for extracting parameters such as WT severely attenuate the true waviness profile of the surface, yielding a WT waviness parameter value that is substantially lower than the actual value.
Applicants of the present invention have recognized that prior filtering and measurement techniques are not sensitive to localized changes in waviness and cannot distinguish or detect regions where waviness changes rapidly. Such filtering and measurement deficiencies were not previously known by those skilled in the art. In addition, Applicants have discovered that the detection of different waviness regions or localized changes in waviness is beneficial in predicting sealing problems between mating surfaces of an assembly, such as between a gasket and one or more mating surfaces.
Before Applicants' invention, there was a need to more accurately determine the waviness of a surface. Moreover, there was a need for improved surface profile data analysis techniques that could detect different waviness regions or localized changes in waviness. In addition, there was a need for improved data analysis techniques to predict gaps between mating part surfaces of an assembly before assembling parts together. Problems associated with the prior art as noted above and other problems are addressed by the Applicants' invention as summarized below.